1. Field of the Invention
This invention relates to safety trigger switches adapted for use on portable electric tools.
2. Description of the Prior Art
The prior art in safety switches for hand held tools has generally provided relatively complicated switches with numerous molded pieces, springs and the like. Most such switches have separate lock and actuator elements that require a manual locking operation. One such switch is described in U.S. Pat. No. 3,780,246. This patent discloses a trigger actuator that is normally biased off and can be manually operated in the "on" position when the operator has his hand on the tool handle. Means is provided to automatically lock the trigger temporarily in the "off" position when the operator moves his hand from the tool handle, and requires intentional release to reactivate the tool. Other similar switches are described in U.S. Pat. Nos. 3,370,475; 3,646,298; 3,854,020 and 3,847,233.
A review of prior art practices shows that there is clearly a need for a double-acting safety switch that automatically assumes a locked position when released by the operator and that is simple to manufacture and compatible with a variety of tool handles.